Re: distortion (domes, etc)

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Glenn Waldron (gwaldron++at++peril.com)
Wed, 19 Feb 1997 09:52:59 -0500

Ken Harris wrote:
>
> We're trying to model distortion. For our application, we're just
> trying to replace the projection function with a non-linear projection
> function, but I seem to recall that performer can handle domes.
[ ... ]
> 3. Render to pbuffer, then texture map that to a (NURBS) surface.
> I don't know if this can be done fast enough. Also there are
> size (we need NTSC video output) and sampling (can I do bilinear interp
> on the fly) problems.

As for sampling, when you render to say the fbuffer, and then use
glCopyTexImage2D to copy into texture memory, only mipmap level 0
is supported on RE/RE2 (anyone know about iR?). So you'd have to
use something like gluBuild2DMipmaps, but this is slow because it calls
glTexImage2D for each mipmap level it generates.

You can still get pretty good performance if you map to a geometric
approx. of a sphere (if you don't mind the approximation). Check out
ftp://ftp.coryphaeus.com/pub/tmp/distcorr.tar.gz for some example code
(requires Coryphaeus EasyScene to run. The math may not be right but
it demonstrates the technique).

Glenn.

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Glenn Waldron - ANSER Leading Edge Technologies phone/PCS: 703.598.7835
email: gwaldron++at++peril.com voice mail: 703.416.8462
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